User`s manual

RabbitFLEX User’s Manual www.rabbit.com 127

ser485Tx

void ser485Tx(void);

DESCRIPTION

Enables the RS-485 transmitter. The brdInit() function must be executed before running this

function. This function is non-reentrant.

After the byte or block of data has been transmitted, the RS-485 transmitter must be idle and its

transmit buffer empty before an application can disable the transmitter and thus receive data from

the RS-485 interface. There are two methods for identifying when to disable the transmitter.

1. Poll the receive data buffer for the transmitted data that is echoed back to it. This is the easier

method. The following code snippet illustrates disabling the transmitter after one byte has been

transmitted using serial port C. You can also send a block of data before disabling the transmit-

ter.

ser485Tx(); // enable transmitter

serCputc ( 0x55 ); // send byte

while (serCgetc() == -1); // wait for echo

ser485Rx(); // disable transmitter

2. Read SxSR, the status register of the serial port you are using. Bits 2 and 3 report on the RS-485

transmitter and its buffer. The following code snippet illustrates how to check these bits if you

are using serial port C.

ser485Tx();

serCputc(0x55);

// Wait for Tx Data buffer to become empty

while(serCwrFree() != COUTBUFSIZE);

// Wait for Tx buffer and shift register on uP to become empty

while(RdPortI(SCSR)&0x08 || RdPortI(SCSR)&0x04);

ser485Rx();

RETURN VALUE

None